Fin-last FinFET and methods of forming same

ABSTRACT

Embodiments of the present disclosure are a FinFET device, and methods of forming a FinFET device. An embodiment is a method for forming a FinFET device, the method comprising forming a semiconductor strip over a semiconductor substrate, wherein the semiconductor strip is disposed in a dielectric layer, forming a gate over the semiconductor strip and the dielectric layer, and forming a first recess and a second recess in the semiconductor strip, wherein the first recess is on an opposite side of the gate from the second recess. The method further comprises forming a source region in the first recess and a drain region in the second recess, and recessing the dielectric layer, wherein a first portion of the semiconductor strip extends above a top surface of the dielectric layer forming a semiconductor fin.

BACKGROUND

The cost and complexity associated with scaling of semiconductor devicesizes according to Moore's law has given rise to new methods to improvesemiconductor device characteristics. New gate materials such as high-kgate dielectrics and metal gates to decrease device leakage, FinFETdevices with increased effective gate area as compared to same-sizeplanar devices, and strain inducing channels for increased chargecarrier mobility are a few examples of methods to continue Moore's Lawscaling for next generation microprocessor designs.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present embodiments, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a perspective view of a FinFET device according to anembodiment;

FIGS. 2A through 5B illustrate in cross-sectional views various stagesin the manufacture of a Fin-Last FinFET device according to anembodiment;

FIGS. 6A through 10C illustrate in cross-sectional views various stagesin the manufacture of a Fin-Last, Gate-Last FinFET device according toanother embodiment;

FIGS. 11A through 16C illustrate in cross-sectional views various stagesin the manufacture of a Fin-Last, Gate-Last, Replacement Channel FinFETdevice according to another embodiment; and

FIGS. 17 through 31 illustrate in cross-sectional views various stagesin the manufacture of a PMOS and an NMOS Fin-Last, Gate-Last,Replacement Channel FinFET device according to another embodiment.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Reference will now be made in detail to embodiments illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts. In the drawings, the shape and thickness may be exaggerated forclarity and convenience. This description will be directed in particularto elements forming part of, or cooperating more directly with, methodsand apparatus in accordance with the present disclosure. It is to beunderstood that elements not specifically shown or described may takevarious forms well known to those skilled in the art. Many alternativesand modifications will be apparent to those skilled in the art, onceinformed by the present disclosure.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment. Thus, the appearances of the phrases “in oneembodiment” or “in an embodiment” in various places throughout thisspecification are not necessarily all referring to the same embodiment.Furthermore, the particular features, structures, or characteristics maybe combined in any suitable manner in one or more embodiments. It shouldbe appreciated that the following figures are not drawn to scale;rather, these figures are merely intended for illustration.

Embodiments will be described with respect to a specific context, namelya FinFET device with a fin-last approach. Other embodiments may also beapplied, however, to planar devices as well as fin devices.

FIG. 1 illustrates a perspective view of a FinFET device 100. The FinFETdevice 100 includes a plurality of semiconductor strips 24 on asemiconductor substrate 20 with a dielectric layer 22 on semiconductorsubstrate 20 and surrounding the semiconductor strips 24. Eachsemiconductor strip 24 may have a fin 29 that is above a top surface ofthe dielectric layer 22. Each fin 29 may have a drain region 28, asource region 30, and a channel region (not shown) disposed between thedrain region 28 and the source region 30. A gate 32 may be disposed overthe channel regions (not shown) of the fins 29. Although FIG. 1illustrates a FinFET device 100 with four fins 29 and a single gate 32,other embodiments with less or more than four fins 29 and more than asingle gate 32 are within the scope of this disclosure.

FIGS. 2A through 5B illustrate in cross-sectional views various stagesin the manufacture of a Fin-Last FinFET device 100 according to anembodiment, with the Figures xA (e.g. 2A) being a cross-sectional viewalong the A-A line and the Figures xB (e.g. 2B) being a cross-sectionalview along the B-B line.

The semiconductor substrate 20 may comprise bulk silicon, doped orundoped, or an active layer of a silicon-on-insulator (SOI) substrate.Generally, an SOI substrate comprises a layer of a semiconductormaterial such as silicon, germanium, silicon germanium, SOI, silicongermanium on insulator (SGOI), or combinations thereof. Other substratesthat may be used include multi-layered substrates, gradient substrates,or hybrid orientation substrates.

The semiconductor substrate 20 may include active devices (not shown inFIG. 2B). As one of ordinary skill in the art will recognize, a widevariety of devices such as transistors, capacitors, resistors,combinations of these, and the like may be used to generate thestructural and functional requirements of the design for the FinFETdevice 100. The devices may be formed using any suitable methods. Thefins 29 may be electrically coupled to the active and passive devices.Only a portion of the semiconductor substrate 20 is illustrated in thefigures, as this is sufficient to fully describe the illustrativeembodiments.

In an embodiment, the semiconductor strips 24 may be formed bypatterning the semiconductor substrate 20. The patterning process may beaccomplished by depositing mask material (not shown) such as photoresistor silicon oxide over the semiconductor substrate 20. The mask materialis then patterned and the semiconductor substrate 20 is etched inaccordance with the pattern. The resulting structure includes aplurality of semiconductor strips 24 formed on the semiconductorsubstrate 20. Each of the plurality of semiconductor strips 24 has asidewall being substantially orthogonal to a top surface of thesemiconductor substrate 20. In some embodiments, the semiconductorsubstrate 20 is etched to a specific depth, meaning the semiconductorstrips 24 are formed to a height, the semiconductor strips 24 may have aheight from about 10 nm to about 500 nm. The semiconductor strips 24 mayhave a width from about 5 nm to 50 nm. The semiconductor strips 24 mayhave a length from about 0.01 um to 10 um. In an alternative embodiment,the semiconductor strips 24 may be epitaxially grown from a top surfaceof the semiconductor substrate 20 within trenches or openings formed ina patterned layer (e.g. the dielectric layer 22) atop the semiconductorsubstrate 20. Because the process is known in the art, the details arenot repeated herein.

The semiconductor strips 24 may be formed of semiconductor material suchas silicon, germanium, silicon germanium, or the like. In an embodiment,the semiconductor strips 24 are silicon. The semiconductor strips 24 maythen doped through an implantation process to introduce p-type or n-typeimpurities into the semiconductor strips 24.

The dielectric layer 22 may blanket deposited on the FinFET device 100.The dielectric layer 22 may be made of one or more suitable dielectricmaterials such as silicon oxide, silicon nitride, low-k dielectrics suchas carbon doped oxides, extremely low-k dielectrics such as porouscarbon doped silicon dioxide, a polymer such as polyimide, combinationsof these, or the like. The dielectric layer 22 may be deposited througha process such as chemical vapor deposition (CVD), or a spin-on-glassprocess, although any acceptable process may be utilized.

After the dielectric layer 22 is deposited, the dielectric layer 22 maybe planarized to level a top surface of dielectric layer 22 and topsurfaces of a hard mask layer (not shown in FIGS. 2A and 2B) on the topsof the semiconductor strips 24. The hard mask layer may be removed by anetch process comprising H₃PO₄ or the like. The dielectric layer 22 maybe planarized in a variety of ways. In an embodiment, the planarizationprocess involves a chemical mechanical polishing (CMP), in which thedielectric layer 22 is reacted and then ground away using an abrasive.This process may continue until the tops of the semiconductor strips 24are exposed. In another embodiment, the dielectric layer 22 may bethinned by a diluted hydrofluoric acid (DHF) treatment or a vaporhydrofluoric acid (VHF) treatment for a suitable time.

After the dielectric layer 22 is planarized, a gate 32 may be formedover the semiconductor strips 24 and the dielectric layer 22. The gate32 may include a gate dielectric layer 26 and gate spacers 34. The gatedielectric layer 26 may be formed by thermal oxidation, CVD, sputtering,or any other methods known and used in the art for forming a gatedielectric. In other embodiments, the gate dielectric layer 26 includesdielectric materials having a high dielectric constant (k value), forexample, greater than 3.9. The materials may include silicon nitrides,oxynitrides, metal oxides such as HfO₂, HfZrO_(x), HfSiO_(x), HfTiO_(x),HfAlO_(x), the like, or combinations and multi-layers thereof.

The gate electrode layer (not shown) may be formed over the gatedielectric layer 26. The gate electrode layer may comprise a conductivematerial and may be selected from a group comprisingpolycrystalline-silicon (poly-Si), poly-crystalline silicon-germanium(poly-SiGe), metallic nitrides, metallic silicides, metallic oxides, andmetals. The gate electrode layer may be deposited by CVD, sputterdeposition, or other techniques known and used in the art for depositingconductive materials. The top surface of the gate electrode layerusually has a non-planar top surface, and may be planarized prior topatterning of the gate electrode layer or gate etch. Ions may or may notbe introduced into the gate electrode layer at this point. Ions may beintroduced, for example, by ion implantation techniques. The gateelectrode layer and the gate dielectric layer may be patterned to formthe gate 32. The gate patterning process may be accomplished bydepositing mask material (not shown) such as photoresist or siliconoxide over the gate electrode layer. The mask material is then patternedand the gate electrode layer is etched in accordance with the pattern.

Gate spacers 34 may be formed on opposite sides of the gate 32. The gatespacers 34 are typically formed by blanket depositing a spacer layer(not shown) on the previously formed structure. In an embodiment, thegate spacers 34 may include a spacer liner 31. The spacer liner 31 maycomprise SiN, SiC, SiGe, oxynitride, oxide, combinations thereof, or thelike. The spacer layer may comprise SiN, oxynitride, SiC, SiON, oxide,combinations thereof, or the like and may be formed by methods utilizedto form such a layer, such as CVD, plasma enhanced CVD (PECVD), lowpressure CVD (LPCVD), atomic layer deposition (ALD), sputter, and othermethods known in the art. The gate spacers 34 are then patterned,preferably by anisotropically etching to remove the spacer layer fromthe horizontal surfaces of the structure.

FIGS. 3A and 3B illustrate the etching of portions of the semiconductorstrips 24 in a strained source drain (SSD) etch step to form recesses 36in the semiconductor strips 24. The SSD etch may selectively etch thesemiconductor strips 24 without etching the dielectric layer 22 or thegate 32 and gate spacers 34. In an embodiment, the recesses 36 may beetched to have a depth from about 5 nm to about 25 nm. The SSD etch stepmay performed in a variety of ways. In an embodiment, the SSD etch stepmay be performed by a dry chemical etch with a plasma source and anetchant gas. The plasma source may be an inductively coupled plasma(ICR) etch, a transformer coupled plasma (TCP) etch, an electroncyclotron resonance (ECR) etch, a reactive ion etch (RIE), or the likeand the etchant gas may be fluorine, chlorine, bromine, combinationsthereof, or the like. In another embodiment, the SSD etch step may beperformed by a wet chemical etch, such as ammonium peroxide mixture(APM), NH₄OH, TMAH, combinations thereof, or the like. In yet anotherembodiment, the SSD etch step may be performed by a combination of a drychemical etch and a wet chemical etch.

After the recesses 36 are formed, the source regions 30 and drainregions 28 may be formed in the recesses 36 as illustrated in FIGS. 4Aand 4B. The source regions 30 and the drain regions 28 may be formed byepitaxially growing SiGe, Si, SiP, combinations thereof, or the like inthe recesses 36 with an optional cap layer of Si over the source regions30 and the drain regions 28. The epitaxial growth of the source regions30 and the drain regions 28 forms a same crystalline orientation in thesemiconductor strip 24, the source regions 30, and the drain regions 28.The growth of the source regions 30 and the drain regions 28 may besubstantially confined by the dielectric layer 22. As illustrated inFIG. 4B, sidewalls of the drain regions 28 may be substantiallyorthogonal to the top surface of the semiconductor substrate 20 and atop surface of the drain regions 28 may substantially parallel with thetop surface of the semiconductor substrate 20. In an embodiment, the topsurface of the drain regions 28 may be substantially coplanar with a topsurface of the dielectric layer 22. In another embodiment, the topsurface of the drain regions 28 may be below or above the top surface ofthe dielectric layer 22. Although FIG. 4B only illustrates the drainregions 28, the source regions 30 have a similar structuralconfiguration on an opposite side of gate 32 such that the descriptionof the drain regions 28 is applicable to the source regions 30 as well.

In a PMOS embodiment, the source regions 30 and the drain regions 28 maycomprise SiGex (where x≧0.1) and may be doped with boron. In an NMOSembodiment, the source regions 30 and the drain regions 28 may compriseSi or SiP and may be doped with phosphorous. In both the NMOS and PMOSembodiments, the source regions 30 and the drain regions 28 may includea Si cap layer over the source regions 30 and the drain regions 28.

FIGS. 5A and 5B illustrate the formation of fins 29. The fins 29 may beformed by etching or recessing the dielectric layer 22 surrounding thesemiconductor strips 24. The portion of the semiconductor strips 24 thatextend above a top surface of the dielectric layer 22 forms the fins 29.In an embodiment, a top surface of the fin 29 may extend above the topsurface of the dielectric layer 22 by about 10 nm to about 30 nm. Thefins 29 may be formed by a chemical oxide reaction such as a CERTAS®etch, a Siconi etch (also referred to as SiCoNi), a DHF treatment,combinations thereof, or the like.

By forming the fins 29 after the source regions 30 and the drain regions28 have been formed, the shape of source regions 30 and the drainregions 28 may be controlled and confined by the dielectric layer 22.This control and confinement will reduce or eliminate the faceting ofthe source regions 30 and the drain regions 28 which will reduce theresistance of the subsequent metal layers contacting the source regions30 and the drain regions 28. Also, the facets on the source regions 30and the drain regions 28 may allow the subsequent metal layers to leakthrough the intersection of the facets.

FIGS. 6A through 10C illustrate in cross-sectional views various stagesin the manufacture of a Fin-Last, Gate-Last FinFET device 150 accordingto another embodiment, with the Figures xA (e.g. 6A) being across-sectional view along the A-A line of FIG. 1, the Figures xB (e.g.6B) being a cross-sectional view along the B-B line of FIG. 1, and theFigure xC (e.g. 6C) being a cross-sectional view along the C-C line ofFIG. 1. Details regarding this embodiment that are similar to those forthe previously described embodiment will not be repeated herein.

The FinFET device 150 in FIGS. 6A through 6C is at a similar stage ofprocessing as the FinFET device 100 in FIGS. 4A and 4B except for theFinFET device 150 has a dummy gate 38 and a dummy gate dielectric layer37 beneath the dummy gate 38. As such, the processing steps up to thisstage are similar to those described in FIGS. 2A through 3B, and are notrepeated herein. The dummy gate dielectric layer 26 may comprise similarmaterials as described in reference to FIGS. 2A and 2B, although anymaterial suitable as a dummy gate dielectric may be used. In anembodiment, the dummy gate 38 may be formed from similar materials asgate 32 or dummy gate 38 may comprise a layer of TiN, TaN, combinationsthereof, or the like on the dummy gate dielectric layer 37 followed by alayer of polysilicon.

FIGS. 7A through 7C illustrate the formation of a etch stop layer (ESL)(not shown) and an inter-layer dielectric (ILD) 40 formed over thesemiconductor substrate 20, the dummy gate 38, spacer liners 31, gatespacers 34, source region 30, and drain region 28. The ESL may beconformally deposited over components on the semiconductor substrate 20.In an embodiment, the ESL is silicon nitride, silicon oxide, the like,or a combination thereof and may be formed by PECVC, LPCVD, ALD, thelike, or a combination thereof.

The ILD 40 may be formed over the ESL. In an embodiment, the ILD 40 maycomprise silicon oxide, silicon nitride, the like, or a combinationthereof. The ILD 40 may be formed by CVD, a high density plasma (HDP),the like, or a combination thereof. The ILD 40 may be planarized to atop surface of the dummy gate 38. In an embodiment, the ILD 40 isplanarized by using a CMP to remove portions of the ILD 40. In otherembodiments, other planarization techniques may be used, such asetching.

FIGS. 8A through 8C illustrate the removal of dummy gate 38 and thedummy gate dielectric layer 37 forming an opening 42 over the channelregion in the semiconductor strip 24 between the source region 30 andthe drain region 28. The dummy gate 38 may be removed by a dry etch thatis selective to the material of the dummy gate 38. For example, if thedummy gate 38 comprises polysilicon, a dry etch using NF₃, SF₆, Cl₂,HBr, the like, or a combination thereof or a wet etch using NH4OH,tetramethylammonium hydroxide (TMAH), the like, or a combination thereofmay be used to remove the dummy gate 38.

After the dummy gate 38 is removed, the fins 29 may be formed by an etchprocess to recess the dielectric layer 22 in the area under the removeddummy gate 38 (see FIG. 9C). This fin formation step may be performed bysimilar processes as described in the fin formation of FIGS. 5A and 5B,and is not repeated herein. In an embodiment, the dielectric layer 22may be recessed beneath the opening 42 (see FIG. 9C), but not in theareas surrounding the source region 30 and the drain region 28 (see FIG.9B).

FIGS. 10A through 10C illustrate the formation of gate dielectric layer44 and gate 46 in the opening 42. The gate dielectric layer 44 and gate46 may be formed of similar materials and by similar processes as gatedielectric layer 26 and gate 32 described in FIGS. 2A and 2B, and arenot repeated herein. As shown in FIG. 10C, the gate 46 and the gatedielectric layer 44 adjoins three sides of the fin 29.

FIGS. 11A through 16CC illustrate in cross-sectional views variousstages in the manufacture of a Fin-Last, Gate-Last, Replacement ChannelFinFET device 200 according to another embodiment, with the Figures xA(e.g. 6A) being a cross-sectional view along the A-A line of FIG. 1, theFigures xB (e.g. 6B) being a cross-sectional view along the B-B line ofFIG. 1, and the Figure xC (e.g. 6C) being a cross-sectional view alongthe C-C line of FIG. 1. Details regarding this embodiment that aresimilar to those for the previously described embodiments will not berepeated herein.

The FinFET device 200 in FIGS. 11A through 11C is at a similar stage ofprocessing as the FinFET device 150 in FIGS. 9A through 9C with thedummy gate and dummy gate dielectric removed to form opening 42. Assuch, the processing steps up to this stage are similar to thosedescribed in FIGS. 2A through 3B and 6A through 9C are not repeatedherein.

FIGS. 12A through 12C illustrate the removal of the channel region byforming an opening 48A in the semiconductor strips 24. The opening 48Amay be formed to a depth of about 5 nm to about 45 nm from a top surfaceof the semiconductor strip 24. The opening 48A may be formed by an etchprocess. In an embodiment, the etch may be performed by a dry chemicaletch with a plasma source and an etchant gas. The plasma source may bean ICR, a TCP, an ECR, a RIE, or the like and the etchant gas may befluorine, chlorine, bromine, combinations thereof, or the like.

FIGS. 13A through 13C illustrate an embodiment wherein another etch isperformed to form opening 48B to have a V-shape below the opening 48A. AV-shape opening may be accomplished by the embodiment that comprises awet chemical etch such as NH₄OH, TMAH, the like, or a combinationthereof. The step of forming opening 48B is optional as the final shapeof the replacement channel opening could be non-V shape (opening 48Aonly) or V-shape (opening 48A in addition to 48B).

After the opening 48A and the optional opening 48B are formed, thereplacement channel 50 may be formed in the opening 48A as illustratedin FIGS. 14A through 14C. The replacement channel region 50 may induce astrain and/or allow higher mobility in the channel region so that theFinFET device 200 may have better device performance. The replacementchannel region 50 may be formed by epitaxially growing SiGe, Si, SiP,Ge, the like, or a combination thereof in the 48A with an optional caplayer of Si over the replacement channel region 50. The growth of thereplacement channel region 50 may be substantially confined by thedielectric layer 22 and the semiconductor strip 24. As illustrated inFIGS. 14A and 14C, sidewalls of the replacement channel region 50 may besubstantially orthogonal to the top surface of the semiconductorsubstrate 20 and a top surface of the replacement channel region 50 maysubstantially parallel with the top surface of the semiconductorsubstrate 20. In an embodiment, the top surface of the replacementchannel region 50 may be substantially coplanar with a top surface ofthe dielectric layer 22 and the top surface of the semiconductor strip24. In another embodiment, the top surface of the replacement channelregion 50 may be below or above the top surface of the dielectric layer22 and the semiconductor strip 24.

In a PMOS embodiment, the replacement channel region 50 may compriseSiGex (where x>0.1) and may be doped with boron. In an NMOS embodiment,the replacement channel region 50 may comprise Si and may be doped withphosphorous. In both the NMOS and PMOS embodiments, the replacementchannel 50 may include a Si cap layer over the replacement channelregion 50.

After the replacement channel region 50 is formed, the fins 29 may beformed by an etch process to recess the dielectric layer 22 in the areaunder the opening 42 as illustrated in FIGS. 15A through 15C. This finformation step may be performed by similar processes as described in thefin formation of FIGS. 5A and 5B, and is not repeated herein. In anembodiment, the dielectric layer 22 may be recessed beneath the opening42 (see FIG. 15C), but not in the areas surrounding the source region 30and the drain region 28 (see FIG. 15B).

FIGS. 16A through 16C illustrate the formation of gate dielectric layer44 and gate 46 in the opening 42 and over the replacement channel region50. The gate dielectric layer 44 and gate 46 may be formed of similarmaterials and by similar processes as gate dielectric layer 26 and gate32 described in FIGS. 2A and 2B, and are not repeated herein. As shownin FIG. 16C, the gate 46 and the gate dielectric layer 44 adjoins threesides of the fin 29.

By forming the fins 29 after the source regions 30 and the drain regions28 have been formed, the shape of source regions 30 and the drainregions 28 may be controlled and confined by the dielectric layer 22.This control and confinement will reduce or eliminate the faceting ofthe source regions 30 and the drain regions 28 which will reduce theresistance of the subsequent metal layers contacting the source regions30 and the drain regions 28. Also, the facets on the source regions 30and the drain regions 28 may allow the subsequent metal layers to leakthrough the intersection of the facets. Further, by replacing thechannel region with a replacement channel region 50, the FinFET device200 may have better performance due to the strain inducing and/or highmobility channel region.

FIGS. 17 through 31 illustrate in cross-sectional views along asemiconductor strip 24 (A-A line of FIG. 1) of various stages in themanufacture of a PMOS FinFET 400 and an NMOS FinFET 300, both in aFin-Last, Gate-Last, Replacement Channel configuration according toanother embodiment. Details regarding this embodiment that are similarto those for the previously described embodiments will not be repeatedherein.

FIG. 17 illustrates an NMOS FinFET 300 and a PMOS FinFET 400 with eachof the NMOS and PMOS FinFETs 300 and 400 comprising a source region 30and a drain region 28. The source regions 30 and the drain region 28 areformed in a semiconductor strip 24 with and ILD 40 formed over thesemiconductor strip 24 and the dummy gates 38.

FIG. 18 illustrates an ESL 60 formed over the ILD 40 and the dummy gates38 and a hard mask layer 62 formed over the ESL 60. The ESL 60 may beformed of an oxide, a nitride, the like, or a combination thereof andthe hard mask layer 62 may be formed of SiN, SiON, SiO₂ the like, or acombination thereof.

In FIG. 19, a bottom anti-reflective coating (BARC) layer 64 is formedover the hard mask layer 62. The BARC layer 64 prevents radiation in asubsequent photolithographic process to reflect off layers below andinterfering with the exposure process. Such interference can increasethe critical dimension of the photolithography process. The BARC layer64 may be formed by CVD, the like, or a combination thereof. Aphotoresist 66 may be deposited and patterned over the BARC layer 64.After developing and removing a portion of the photoresist 66, an etchstep is further performed into the BARC layer 64 to expose the portionof the hard mask layer 62 over the NMOS FinFET 300. FIG. 20 illustratesthe transferring of the photoresist 66 pattern to the hard mask layer 62to expose the NMOS FinFET 300.

In FIG. 21, the dummy gate 38 of the NMOS FinFET 300 is removed and achannel region below the dummy gate 38 is removed. A first etch may beperformed to form opening 68 and a second etch may be performed to formopening 70 in the semiconductor strip 24. This step may be performed ina similar manner as described above in reference to FIGS. 12A through12C and will not be repeated herein. FIG. 22 illustrates the formationof a V-shape opening 72 below the opening 70. This step may be performedin a similar manner as described above in reference to FIGS. 13A through13C and will not be repeated herein.

FIG. 23 illustrates the formation of a V-shaped NMOS replacement channelregion 74 in the openings 70 and 72. This step may be performed in asimilar manner as described above in reference to FIGS. 14A through 14Cand will not be repeated herein. FIG. 24 illustrates the removal of thehard mask layer 62 and the ESL 60 over the PMOS FinFET device 400. Thisstep may be performed by an etch comprising H₃PO₄, a DHF treatment, thelike, or a combination thereof.

FIG. 25 illustrates the formation of another ESL 76 and a hard masklayer 78 over the ILD 40 and the NMOS and PMOS FinFETs 300 and 400. TheESL 76 and the hard mask layer 78 may be deposited in the opening 68,wherein the ESL 76 adjoins the gate spacers 34 and at top surface of theV-shaped NMOS replacement channel region 74. This step may be performedin a similar manner as described above in reference to FIG. 18 and willnot be repeated herein. FIG. 26 illustrates the formation of anotherBARC layer 80 and a photoresist 82 that is patterned to expose the hardmask layer 78 over the PMOS FinFET 400. This step may be performed in asimilar manner as described above in reference to FIG. 19 and will notbe repeated herein. FIG. 27 illustrates the patterning of the hard masklayer 78 and the ESL 76 to expose the dummy gate 38 over the PMOS FinFET400. This step may be performed in a similar manner as described abovein reference to FIG. 20 and will not be repeated herein.

FIG. 28 illustrates the removal of the dummy gate 38 over the PMOSFinFET 400 and a channel region below the dummy gate 38 is removed. Thisstep may be performed in a similar manner as described above inreference to FIG. 21 and will not be repeated herein. FIG. 29illustrates the formation of PMOS replacement channel region 84 in theopening 83. This step may be performed in a similar manner as describedabove in reference to FIGS. 14A through 14C and will not be repeatedherein. In an embodiment, the PMOS replacement channel region 84 mayhave a shallower depth than the NMOS replacement channel region 74 (seeFIG. 29). In another embodiment, the PMOS replacement channel region 84may have a different shape than the NMOS replacement channel region 74(see FIG. 29). As described above in reference to FIGS. 14A through 14C,the NMOS replacement channel region 74 may comprise different materialsthan the PMOS replacement channel region 84, although the materials maybe the same. In another embodiment, the processing flow may form theNMOS FinFET 300 first or the PMOS FinFET 400 first.

FIG. 30 illustrates the removal of the hard mask layer 78 and the ESL76. This step may be performed in a similar manner as described above inreference to FIG. 24 and will not be repeated herein. After the removalof the hard mask layer 78 and the ESL 76, the fins may be formed byrecessing the dielectric layer (not shown) surround the semiconductorstrips 24. This step may be performed in a similar manner as describedabove in reference to FIGS. 15A through 15C and will not be repeatedherein. FIG. 31 illustrates the formation of the gate dielectric layer86 and the gates 88 over the NMOS replacement channel region 74 and thePMOS replacement channel region 84. This step may be performed in asimilar manner as described above in reference to FIGS. 16A through 16Cand will not be repeated herein.

An embodiment is a method for forming a FinFET device, the methodcomprising forming a semiconductor strip over a semiconductor substrate,wherein the semiconductor strip is disposed in a dielectric layer,forming a gate over the semiconductor strip and the dielectric layer,and forming a first recess and a second recess in the semiconductorstrip, wherein the first recess is on an opposite side of the gate fromthe second recess. The method further comprises forming a source regionin the first recess and a drain region in the second recess, andrecessing the dielectric layer, wherein a first portion of thesemiconductor strip extends above a top surface of the dielectric layerforming a semiconductor fin.

Another embodiment is a method of forming a FinFET device, the methodcomprising forming a semiconductor strip over a semiconductor substrate,wherein the semiconductor strip is disposed in a dielectric layer,forming a first dummy gate over the semiconductor strip and thedielectric layer, forming a first set of gate spacers on opposite sidesof the first dummy gate, etching recesses in the semiconductor strip,and epitaxially growing a first source region in one of the recesses anda first drain region in another one of the recesses. The method furthercomprises removing the first dummy gate to expose a first channel regionin the semiconductor strip, removing the first channel region in thesemiconductor strip, forming a first replacement channel region in thesemiconductor strip, etching the dielectric layer, wherein the firstreplacement channel region extends above a top surface of the dielectriclayer, and wherein a portion of the semiconductor strip extends abovethe top surface of the dielectric layer forming a semiconductor fin, andforming a first active gate over the first replacement channel region.

Yet another embodiment is a FinFET device comprising a dielectric layeron a semiconductor substrate, a semiconductor fin extending from thesemiconductor substrate, wherein the semiconductor fin is disposed inthe dielectric layer, and a first source region and a first drain regiondisposed in the semiconductor fin, wherein the first source region andthe first drain region comprise a first epitaxial material, wherein thefirst source region and the first drain region have sidewalls that aresubstantially orthogonal to a top surface of the semiconductorsubstrate. The FinFET device further comprises a first channel region inthe semiconductor fin, wherein the first channel region is laterallybetween the first source region and the first drain region, and a firstgate structure over the semiconductor fin, wherein the first gatestructure is over the first channel region.

Although the present embodiments and their advantages have beendescribed in detail, it should be understood that various changes,substitutions, and alterations can be made herein without departing fromthe spirit and scope of the disclosure as defined by the appendedclaims. Moreover, the scope of the present application is not intendedto be limited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods, and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed, that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present disclosure.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps.

What is claimed is:
 1. A method for forming a FinFET device, the methodcomprising: forming a semiconductor strip over a semiconductorsubstrate, wherein the semiconductor strip is disposed in a dielectriclayer; forming a gate over the semiconductor strip and the dielectriclayer; forming a first recess and a second recess in the semiconductorstrip, wherein the first recess is on an opposite side of the gate fromthe second recess; forming a source region in the first recess and adrain region in the second recess; and recessing the dielectric layer,wherein a first portion of the semiconductor strip extends above a topsurface of the dielectric layer forming a semiconductor fin.
 2. Themethod of claim 1, wherein the source region and the drain region havesidewalls substantially orthogonal to a top surface of the semiconductorsubstrate.
 3. The method of claim 1, wherein the source region and thedrain region have top surfaces substantially parallel to a top surfaceof the semiconductor substrate.
 4. The method of claim 1, wherein thefirst portion of the semiconductor strip comprises the source region andthe drain region.
 5. The method of claim 1, wherein the forming thesource region in the first recess and the drain region in the secondrecess further comprises epitaxially growing the source region in thefirst recess and the drain region in the second recess.
 6. The method ofclaim 1 further comprising: before the step of recessing the dielectriclayer, forming gate spacers on opposite sides of the gate; depositing anetch stop layer (ESL) over the semiconductor strip, the gate, the sourceregion, the drain region, and the dielectric layer; depositing aninter-layer dielectric (ILD) over the ESL; planarizing the ILD and theESL to expose a top surface of the gate; removing the gate to form anopening between the gate spacers; performing the step of recessing thedielectric layer, wherein the dielectric layer is recessed below theopening between the gate spacers; and forming a second gate in theopening between the gate spacers.
 7. The method of claim 1, wherein therecessing the dielectric layer comprises performing a chemical oxidereaction comprising a CERTAS® etch, a Siconi etch, a DHF treatment, or acombination thereof.
 8. A method of forming a FinFET device, the methodcomprising: forming a semiconductor strip over a semiconductorsubstrate, wherein the semiconductor strip is disposed in a dielectriclayer; forming a first dummy gate over the semiconductor strip and thedielectric layer; forming a first set of gate spacers on opposite sidesof the first dummy gate; etching recesses in the semiconductor strip;epitaxially growing a first source region in one of the recesses and afirst drain region in another one of the recesses; removing the firstdummy gate to expose a first channel region in the semiconductor strip;removing the first channel region in the semiconductor strip; forming afirst replacement channel region in the semiconductor strip; etching thedielectric layer, wherein the first replacement channel region extendsabove a top surface of the dielectric layer, and wherein a portion ofthe semiconductor strip extends above the top surface of the dielectriclayer forming a semiconductor fin; and forming a first active gate overthe first replacement channel region.
 9. The method of claim 8, whereinthe forming the first replacement channel region in the semiconductorstrip comprises epitaxially growing the first replacement channel regionin the semiconductor strip.
 10. The method of claim 8, wherein the firstreplacement channel region has a V-shaped bottom surface extending intothe semiconductor strip.
 11. The method of claim 8, wherein the firstreplacement channel region has a substantially planar bottom surfacethat is substantially parallel to a top surface of the semiconductorsubstrate.
 12. The method of claim 8 further comprising: before the stepof etching the dielectric layer, forming a second dummy gate over thesemiconductor fin; forming a second set of gate spacers on oppositesides of the second dummy gate; epitaxially growing a second sourceregion in one of the recesses and a second drain region in another oneof the recesses; after the step of forming the first replacement channelregion, removing the second dummy gate to expose a second channel regionin the semiconductor strip; removing the second channel region in thesemiconductor strip; forming a second replacement channel region in thesemiconductor strip; performing the step of etching the dielectriclayer, wherein the first replacement channel region and the secondreplacement channel region extend above a top surface of the dielectriclayer; and forming a second active gate over the second replacementchannel region.
 13. The method of claim 12, wherein the firstreplacement channel region comprises a different material than thesecond replacement channel region.
 14. The method of claim 12, whereinthe first replacement channel region has a V-shaped bottom surfaceextending into the semiconductor strip, and wherein the secondreplacement channel region has a substantially planar bottom surfacethat is substantially parallel to a top surface of the semiconductorsubstrate.
 15. The method of claim 12, wherein the first replacementchannel region has a shallower depth than the second replacement channelregion.
 16. The method of claim 12, wherein the first source region, thefirst drain region, the first active gate, and the first replacementchannel region forms an NMOS FinFET device, and wherein the secondsource region, the second drain region, the second active gate, and thesecond replacement channel region forms a PMOS FinFET device.
 17. Amethod comprising: forming a semiconductor strip in a dielectric layerover a semiconductor substrate; forming a first gate over a firstchannel region in the semiconductor strip; forming recesses in thesemiconductor strip, the recesses being on opposites sides of the firstchannel region; forming a source region in one of the recesses and adrain region in another one of the recesses; and recessing thedielectric layer to expose a top portion of the semiconductor stripabove a top surface of the recessed dielectric layer, the top portion ofthe semiconductor strip forming a semiconductor fin.
 18. The method ofclaim 17 further comprising: forming gate spacers on opposite sides ofthe first gate; before the step of recessing the dielectric layer,removing the first gate to form an opening between the gate spacers; andafter the step of recessing the dielectric layer, forming a second gatein the opening between the gate spacers.
 19. The method of claim 18further comprising before forming the second gate in the opening betweenthe gate spacers, replacing the first channel region in thesemiconductor strip with a second channel region in the semiconductorstrip.
 20. The method of claim 17, wherein the source region and thedrain region have sidewalls substantially orthogonal to a top surface ofthe semiconductor substrate, and wherein the source region and the drainregion have top surfaces substantially parallel to the top surface ofthe semiconductor substrate.